Code obfuscation is a general name for techniques for converting a program of instructions for a computer in a way that obscures its content. Code obfuscation may be applied to make it more difficult to identify the relevant part of the program needed to execute a program on an unlicensed type of computer or without protection measures.
U.S. Pat. No. 6,779,114 describes a code obfuscation technique that involves obscuring control flow of a program. Branch instructions are added to lumps of instructions in a way that obscures the intended execution order of the lumps. U.S. Pat. No. 5,559,884 describes pseudo-random reordering of basic blocks of a program to create a signature that can be used to identify a source through which the program has been distributed.
Many modern processors use instruction caching, pre-fetching and/or pipelining techniques, which rely on locality of program flow. The addition of branch instructions with obscure targets reduces locality, which may have the effect of preventing some of the gain in execution speed that is expected from such techniques.